1. Field of the Invention
The field of the present invention relates generally to devices for use in endoscopic examinations of the human colon. More specifically, the device described herein relates to medical equipment to facilitate the insertion of an endoscope into the human colon by keeping the sigmoid colon in a straightened position. Even more specifically, this device relates to splints or overtubes used over and in conjunction with an endoscope to maintain straightness of the sigmoid colon for the purpose of facilitating the insertion and movement of the endoscope through the sigmoid colon.
2. Background
As used herein, the term "splint" is used interchangeably with the term "overtube" to generally describe the device that is the subject of this patent. The term "endoscope" or "scope" is used to refer to a colonoscope, gastroscope, enteroscope, or other types of medical endoscopes. In referring to the opposite ends of the splint or scope, the "proximal end" means that part of the splint or scope which is closest to the operator or physician/surgeon performing the endoscopy and the "distal end" means that part of the splint or scope farthest from the operator or physician/surgeon.
Colonoscopy is the most sensitive and specific means for examining the colon, particularly for the diagnosis of colon cancers and polyps. Because the cecum, the portion of the colon furthest from the anus, is a common location for cancer, it is important that the entire colon be completely examined. In addition, Western countries have experienced a "rightward shift" of cancers of the colon in recent years as cancers of the right colon have become more common. However, because the anatomy of the colon can extremely vary from person to person, the technique of total colonoscopy is technically demanding.
During a colonoscopy, the scope is inserted in the anus, through the rectum, sigmoid colon, descending colon, transverse colon, ascending colon and then into the cecum. Advancing the scope, which is typically about 160 centimeters in length, can be difficult due to a loop in the sigmoid colon. Once the scope reaches the descending colon or transverse colon, this loop must be reduced by withdrawing the scope to a straightened position. Failure to straighten the loop in the sigmoid colon prior to continuing can cause enlargement of the loop and result in pain and damage, including adverse cardiac reactions such as hypotension and bradycardia. Once the loop is straightened, further advancement of the endoscope can usually be accomplished.
In patients having long sigmoid colons, reaching the cecum may be extremely difficult, if not impossible, due to reformation of the sigmoid loop when the operator attempts further advancement of the scope. Continued pushing of the scope under these circumstances enlarges the loop, rather than advancing the tip of the scope. Scope operators often employ various maneuvers to complete the examination, including changing the patient's position and the use of abdominal compressions. Unfortunately, these maneuvers prolong the procedure and are not always successful in helping the scope reach the cecum. Even expert colonoscopists experience difficulties in 10-20% of cases because of the long sigmoid colon problem. The overall success rate for total colonoscopy, i.e. getting the tip of the colonoscope to the cecum, has been reported to be 55-98%.
3. Related Art
The existing sigmoid splint has been in existence for over twenty years. When used correctly, it has proven to be a very helpful tool by allowing successful examination to the cecum, speeding up the procedure and making it less painful to the patient. The prior art splint is a hollow cylinder about 40 centimeters in length. It is made of a flexible but slightly rigid material, such as plastic, polyethylene, polyurethane, vinyl, or polyvinyl, of about 1 millimeter in thickness. The distal end of the prior art splint is tapered to an inner diameter about 4 millimeter greater than the scope. The proximal end has an outer diameter that is much larger than the distal end to prevent complete entry of the splint into the patient's body. The proximal end also has a rubber diaphragm with a hole slightly larger in diameter than the outside diameter of the scope to allow easy insertion of the scope through the splint.
In use during a colonoscopy, the colonoscope is inserted into the colon until further progress becomes difficult, at which time the tip of the colonoscope is typically located in the upper descending colon or the transverse colon. Using the colonoscope itself, the sigmoid loop is initially straightened. The splint, which should be placed over the proximal shaft of the colonoscope prior to beginning the examination, is gently pushed into the colon over the scope with the aid of lubricants, such as "JOHNSON & JOHNSON K-Y JELLY" (a registered trademark of Johnson & Johnson). With full insertion of the splint, the proximal end of the splint remains outside the anus, while the distal end is in the descending colon. The placement of the splint allows and maintains an almost straight-line passage from the anus to the descending colon. The colonoscope is then advanced while the splint is held stationary. The splint keeps the sigmoid in a straightened position, prevents a loop from reforming and facilitates advancement of the scope to the cecum.
Despite its advantages, the prior art splint is very rarely utilized due to the risk of perforation of the colon by the splint. Perforations are caused by the entrapment of a piece of colonic wall between the distal end of the splint and the endoscope when the splint is moved inside the patient's colon. The entrapment can occur either when the splint is advanced over the scope or when the scope is withdrawn through the splint. Once entrapped, a piece of colonic wall can be sheared off by the relatively sharp edge of the distal end of the splint. If the entrapped piece of colonic lining includes all layers of the colonic wall, then the tear becomes a through and through perforation. Alternatively, when the splint is advanced, carrying with it a piece of entrapped mucosa, the colonic wall behind it can be torn, also resulting in a perforation.
In the prior art devices, the space between the scope and the splint, approximately 2 millimeter in radius, has to exist to allow smooth movement of the scope and the splint against each other. Without this space, i.e., by modifying the prior art splint to have a tight fit for the scope, three undesirable features would occur: 1) too much friction would occur between the scope and the splint, causing resistance to manipulations; 2) damage to the scope as the splint rubs against the surface of the scope; and 3) the lubricant would be erased off the scope. In the invention which is the subject of the present patent, the space between the scope and the distal end of the splint is eliminated and the problems of friction to the movement of the endoscope against the splint, and its potential damage to the scope and the erasure of the lubricant, are avoided.
A safe sigmoid splint has very important applications in colonoscopy, and can lead to radical changes in the manner in which colonoscopy is performed. Currently, colonoscopes have to be fairly large (e.g., over 13 mm in outer diameter) in order to be able to produce the rigidity necessary to hold the sigmoid straight. Even with these large diameter, rigid scopes, the problem of reformation of the sigmoid loop still arises on a not infrequent basis. Reformation of the sigmoid loop not only causes great difficulties in advancing the tip of the scope, but is also extremely painful to the patient, such that intravenous sedation is almost always necessary. With a splint device, a much smaller colonoscope can be used, which could be almost painless to the patient. The reduction in pain results from reduced stretching of the sigmoid loop upon advancement to the descending colon and due to the sigmoid loop only being formed once during the procedure.
U.S. Pat. No. 5,337,733 to Bauerfeind, et al. describes a tubular inserting device with variable rigidity. This long overtube is made of two thin walls with space between. The outer wall is made of semi-rigid, non-expandable material, while the inner wall is made of material which is radially deformable, allowing expansion and resolution of the intervening space. Fluid is injected into the proximal end of the overtube to expand the space. When the space is expanded, the two walls separate from each other creating a flexible overtube. Suctioning out the injected fluid removes the space, bringing the two walls into contact with each other. The external surface of the inner wall and the internal surface of the outer wall are lined with a cogwheel like arrangement that engage and lock against each other when the space between them is removed, thereby producing a rigid overtube. When the space is expanded by injecting fluid, the two walls separate and the overtube returns to its flexible state.
The Bauerfeind, et al. overtube is introduced over the endoscope. During the colonoscopy procedure, when flexibility of the overtube is desired, the space between the two walls is expanded. When rigidity of the overtube is desired, this space is eliminated. The invention described by Bauerfeind, et al. in U.S. Pat. No. 5,337,733 does not address the issue of entrapment of colonic wall material between the distal edge of the splint and the scope. Tight-fitting seals, as described in the present invention, would not function properly in the Bauerfeind, et al. device, as it would create too much friction between the inside wall of the overtube and the endoscope. The present invention is much shorter, consists of only one wall and aims to address the problems caused by the space between the distal edge of the splint and the colonoscope.
Another invention, U.S. Pat. No. 3,805,770 to Okada, describes a ring-like device to hold the anus open for insertion of an endoscope past the anal sphincter. As with the Bauerfeind, et al. overtube, the Okada device does not utilize a tight-fitting seal and a tight-fitting seal would be detrimental to the proper function of the Okada invention. A tight-fitting seal would wipe off the lubricants placed on the endoscope, thereby defeating the very purpose for utilizing the device disclosed by Okada.
Another invention, U.S. Pat. No. 5,259,366 to Reydel, describes an endoscopic treatment procedure that utilizes a catheter sleeve assembly that slides along the outer surface of an endoscope to provide at least one lumen for inserting medical instruments into the patient's body. This device does not utilize a sealing mechanism to prevent colonic wall entrapment and is not intended to straighten the sigmoid colon.
Yet another invention, U.S. Pat. No. 4,601,283 to Chikama, describes the use of a wire made of memory shape alloy. This wire is inserted into the biopsy channel of the scope. By keeping the wire at certain temperatures, it returns and remains in its "memorized" straight shape, keeping the endoscope in a straightened position. The present invention avoids the necessity of the special wire and avoids the resultant possible damage to the biopsy channel, which has been reported to occur.